Large piston engines, such as ship and power plant engines, are usually provided with turbochargers for increasing the pressure of the intake air. Because of the high intake air pressures, effective cooling of the intake air is needed to keep the temperature of the intake air after the turbocharger at an acceptable level. The intake air system therefore comprises one or more charge air coolers, which usually utilize cooling water for absorbing heat from the intake air. Commonly, the charge air cooling takes place in two stages. In the first stage, high-temperature cooling water is used for initial cooling of the intake air and in the second stage low-temperature cooling water is used for the final cooling of the intake air.
The charge air coolers are mounted inside air cooler housings. An air duct is connected to an outer side of the air cooler housing for introducing the intake air into the charge air cooler. A seal is needed between the air duct and the air cooler housing. The charge air cooler is connected to the air cooler housing and a seal is arranged in the joint between the charge air cooler and the air cooler housing. The air cooler housing is usually manufactured by casting. However, in order to ensure effective sealing between the air cooler housing and the charge air cooler and between the air cooler housing and the air duct, those surfaces of the air cooler housing that form part of the joints between the air cooler housing and the adjacent components need to be machined. This is a problem especially in the case of the surface against which the charge air cooler is arranged. Since the surface is inside the air cooler housing, machining of the surface is both complicated and slow. Good surface quality and small tolerances are difficult to reach, and therefore the joint between the charge air cooler and the air cooler housing is exposed to air leakages. The need to machine the inner surface of the air cooler housing also increases the manufacturing costs.